Earlier work led to the view that orientation perception develops in stages--first the child distinguishes only between upright and non-upright shapes, then the child differentiates the non-upright category into inverted and sideways, and finally the sideways category is divided into left and right. The predictions stemming from this theoretical approach will be investigated through the use of a series of discrimination problems presented to children between two and eight years, and the use of the reaction-time method with older subjects. Additional techniques will be developed for further work with the children of two years. Another set of studies explores the orientational characteristics of representations in visual memory in children and adults, and the problem is approached in a number of different ways. The role of stimulus orientation in the storage of items in short-term, and long-term memory will be investigated through the use of brief stimulus presentations and a reaction time response measure, and the use of a task involving recognition memory for a large series of picture. In addition, information will be obtained through the copying of shapes, and the descriptions of images aroused by specific verbal cues.